Please join us for drinks and dinner on the upper patio
Dress is casual and you may want to bring a jacket as we will be on the patio (with heaters)
The restaurant is a short distance from the Tucson Marriott University Park and can be accessed by public transportation
The cost will be $20 per person (please be prepared to pay with cash or check)
Please confirm with Julie Hamilton via email (Julie.hamilton@amecfw.com) or phone (602-418-3950) by February 6, 2015

Walter Heinrichs, Jr.
We received just a brief note that Walter E. Heinrichs, Jr., CPG-688, one of Arizona's best known mining geologists, passed away on Thursday, October 10, 2013. Photo of Lee Allison presenting the Arizona Geological Society's Honorary Lifetime Membership to Walt in 2008.

There will be two stops with walks up to 1 mile in length and 100-200 feet elevation gains. All of the stops are at parking lots, so the folks who don’t care to make the walk have the opportunity to wait in the parking lot. We will have a lunch break at the Gordon Hirabayashi campground, where there are restrooms and picnic benches.

Field trip participants should bring their own snacks/lunch. We will be meeting at a shopping plaza that includes a grocery store and a café. We will be carpooling from the shopping plaza, since parking at the various stops will be limited.

There is no charge for the field trip, but please RSVP to James Adu (AIPG secretary) at (520) 405-3656 or adunkansah@yahoo.co.uk by April 9, so we can have estimate for parking spaces and handouts.

References: OFR-06-01-A Geologist's Guide to the Core Complex Geology Along the Catalina Highway, Tucson Area, Arizona, v. 1.1, by J.E. Spencer, 2006, 38 p. This can be downloaded without charge from the AZGS website (http://repository.azgs.az.gov/sites/default/files/dlio/files/nid360/ofr_06-01catalinafieldguide-colorprint.pdf). Please download a copy should you want to have it as a reference during the field trip. Jon will bring a small handout for that day.

A natural history of the Santa Catalina Mountains, Arizona, with a introduction to the Madrean sky Islands, Richard c. Brusca and Wendy Moore, Arizona-Sonora Desert Museum Press, 232 p.

The Arizona Section hosted the Fall 2013 field trip in northern Arizona on Saturday, October 5th. Section member Paul Lindberg (CPG-06344) prepared the 9-page color guidebook and road log, and led 21 participants on the field trip. The trip circumnavigated the northern portion of what is probably one of the youngest Basin and Range grabens to cut the Mogollon Rim. The Oak Creek - Mormon Lake Graben is a Pliocene-age (2 to 3Ma) structure identified by Paul during his many years of exploring and geologic mapping of the area south of Flagstaff and east of Sedona.

The field trip made a counter-clockwise tour around the northern end of the graben to study faults, rock exposures, fault outcrops, and other physical features related to rift valley genesis. We first visited a fault scarp within the graben that has been breached by an active stream channel that drains the Munds Park area. The next stop was a viewpoint on Interstate 17 that afforded a view to the west of Jacks Canyon fault that is the southward continuation of the Oak Creek fault - the west graben boundary. Traveling south and then east, we stopped to look at Stoneman Lake, a nearly mile-wide, roughly circular depression in the graben. The origin of the depression is uncertain; it may be a small graben within the graben, or an area of basalt collapse into a lava tube.

The trip continued to Mormon Lake, where another viewpoint afforded a panoramic view of the east side of the Mormon Lake depression, which forms the eastern boundary of the graben. Paul discussed the drainage changes that resulted from the crustal stretching of this part of the continent. The next stop was at a spectacular hands-on fault scarp where down-dropped Miocene basalt lava on the west side of the fault is in contact with Permian Kaibab Limestone on the east side of the fault (Photograph #1).

The tour then passed through the southern side of Flagstaff, which lies within the shallow northern part of the graben. Then we headed south into Oak Creek Canyon to observe two ages of fault movement along the Oak Creek fault zone. One phase is Laramide age (~70 Ma) compression where high-angle reverse faulting raised the east side of Oak Creek Canyon. Evidence for this phase included fault drag on the west side of the fault zone visible along Oak Creek (Photograph #2). The much younger (2 to 3 Ma) superimposed reactivation of the modern normal phase of the Oak Creek fault dropped the east side back down. Evidence for this phase included younger basalt on the east side of the fault juxtaposed against older (Permian) sedimentary rocks, and bleaching of the normally red sandstones by fluids migrating along the fault zone.

Photograph #2: Fault drag is down-to-the west on opposite bank of north to south flowing Oak Creek. Fault is behind the photographer.

Then we drove up Airport Mesa in Sedona for an aerial view of the Sedona area (Photograph #3). Paul pointed out the difference in erosional character between the now-dry stream-cut valleys in the Sedona area, and the young V-shaped Oak Creek Canyon and other smaller canyons that drain off the graben. We left Airport Mesa traveling south on Highway 179 and made two additional stops to look at graben-related features. One unanswered question was the true origin of the “exotic gravels, Beavertail Gravels, and Rim Gravels” that are present in the study area. Previous workers suggested the gravels are different units that were deposited from north-to-south off the rim. Paul’s studies suggest the gravels are correlative as one unit with a common source, and were transported from south to north. The highlands source was eroded away prior to formation of the graben. Local outcrops are now observed stair-stepping down to the south as a result of formation of the graben.

Photograph #3: Sedona area viewed from Airport Mesa northward

At each field trip stop, we had a lively discussion on the geology of the area. Paul noted that additional work needs to be done in the area to firm up some of his interpretations, including a few more basalt age-dates to clarify the stratigraphic and structural relationships. Anyone need a thesis topic?